one person who was close to him said he got the sense that senator obama really wondered if he would be able to continue in politics >> reporter: and it raised real problems with his wife michelle >> the bobby rush race was the nadir of the obama marriage. her feeling was, why are you doing this? this is the moment when they want two totally different things. you know, barack obama wants political success. and his wife wants a normal life. i asked the preside and fst lady how longt had taken them to recover from that period? they said two to three years. so this is a serious toll on their relationship. >> woodruff: the choice: 2012 >> woodruff: "the choice 2012" airs on most pbs stations tonight. >> ifill: next, our series on "coping with climate change" looks at how the city of chicago is dealing with ever warmer temperatures, by trying to cool things down with changes to its landscape. we turn again to hari sreenivasan, who traveled there recently. >> that's your grandfather. >> sreenivasan: 15-year-old janell coleman only knows her grandfather through the photographs that her gran